A Tissue &Experimental Modeling Core will coordinate specialized tissue preparations and animal models, and will serve Projects 1, 2, and 3 of the University of Iowa CORT. All animal modeling studies will be managed by this Core, to maximize the efficiency in time, cost, and effort. This Core will provide two survival animal models: a porcine knee model of blunt impaction cartilage injury (the associated studies are proposed in Projects 1, 2, and 3), and a rabbit knee model of blunt impaction with joint instability (forProject 2). Surgical insults for these models will be applied arthroscopically, to minimize potential effects of surgical invasion itself. Impaction insults will be performed using a custom-designed device that allows delivery of a compressive force pulse of prescribed energy magnitude. The force transmission during the impaction will be monitored, allowing accurate measurement of energy absorption, the peak cartilage stress level, and the rate of cartilage stress elevation. All tissue collection from experimental animals, including cartilage and serum samples, and the processing and storing of these samples, will also be managed by this Core. Cartilage sample preparations for ex vivo studies in Projects 1, 2, and 3, namely the modeling of blunt impaction cartilage damage associated with intraarticular fractures or bone bruises, will also be provided by this Core. Another objective of this Core is to facilitate preparation for future studies. To this end, this Core aims to pilot an animal model of human intraarticular fracture that naturally develops post-traumatic osteoarthritis (PTOA). This model will allow not only longitudinal study of the disease progression processes of PTOA secondary to intraarticular fractures, but will also allow future studies of the organ-level therapeutic effects of new treatment paradigms, including bio-pharmaceutical interventions that will be studied in Projects 1 and 2. A porcine model of knee instability will also be piloted. In addition to these tasks, this Core will collect and store serum samples from all patients in Projects 3 and 4, to enable future studies of possible genetic risk factors for post-traumatic OA in humans.